Apache2::Translation::BDB - A provider for Apache2::Translation
<TranslationProvider BDB> BDBEnv /path/to/directory ReadOnly 1 </TranslationProvider> or $provider=Apache2::Translation::BDB->new(BDBEnv=>..., ...); $provider->start; $provider->stop;
BDB provider implements the
Apache2::Translation provider interface as documented in Apache2::Translation::_base. It provides for all optional functions.
Other than the
BDB doesn't implement a cache. BerkeleyDB is fast enough on its own. Neither does it monitor the timestamp of a file on disk. Hence it doesn't need a
Nevertheless it implements a
timestamp method that can be used by external tools to synchronize the database state with external sources.
Here you can pass a directory name or a
BerkeleyDB::Env object. In the latter case, the environment must be initialized with DB_INIT_MPOOL, DB_INIT_LOCK, DB_INIT_TXN and DB_INIT_LOG. Further, you need to specify a deadlock detection method.
If a directory is passed (the normal case) the provider initializes the environment if it is not already set up. It creates 3 databases,
Apache2::Translation::BDB-keyuri.db is used as an associated database for
Apache2::Translation::BDB-id.db. That means it is a secondary index.
The extra database holds only the timestamp value. But the provider offers an
extra method to store more information in this database.
See CONFIGFURATION below for performance tuning.
If set to true the databases are opened in readonly mode. Please note that the program needs write permission to the database files even if this flag is set.
BerkeleyDB supports nested transactions. If you provide a parent transaction the provider wraps its changes in a child transaction. Otherwise it works in an unrelated transaction.
returns the database handle of the extra database.
stores and retrieves information from the extra database. If value is given it is written as value for the key to the database.
returns the previous value of the key.
Note, the key
\ttmstmp is reserved.
sets or retrieves the timestamp from the extra database.
A Berkeley database is configured and tuned via a config file named
DB_CONFIG located in the environment directory. The default parameters are quite small for a WEB server application where many processes access the database in parallel.
To tune your database create an empty directory and within it a file named
DB_CONFIG. Then start the WEB Server or a helper program to create and initialize the databases.
For me I found these values sufficient for a fairly large WEB Server:
set_lk_max_locks 5000 set_lk_max_lockers 5000 set_lk_max_objects 5000 set_tx_max 200 set_flags DB_LOG_INMEMORY set_lg_regionmax 1048576 set_lg_bsize 10485760
See http://www.oracle.com/technology/documentation/berkeley-db/db/ref/toc.html for further information.
Torsten Foertsch, <email@example.com>
Copyright (C) 2005-2008 by Torsten Foertsch
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.